Radio telephone system



20, 1940- D. A. HEISNER 2,211,894

RADIO TELEPHONE SYSTEI Filed 001;. 14, 193' 3 Sheets-Sheet 1 N AT TOEN EYS 0, 1940. D. A. HEISNER RADIO TELEPHONE SYSTEI Filed Oct. 14, 193'1 3 Sheets-Sheet 2 VWN INVEHTTOE.

A'T TOKH EYs IuWN Ed DONALD A. HEaaNEIe.

Aug. 20, 1940. o. A. HEISNER RADIO TELEPHONE SYSTEM Filed Oct. 14, 193'? 3 Sheets-Sheet 3 from Patented Aug. 20, 1940 UNITED STATES RADIO TELEPHONE SYSTEM Donald A. Heisner, Lorain, Ohio, assignor to The Lorain Telephone Company, Lorain, Ohio, a

corporation of Ohio Application October 14, 1937, Serial No. 168,988

13 Claims.

This invention relates to radio communication systems, and in particular to radio telephone circuits.

One object of this invention is to provide a system for controlling radio telephone receivers a remote location, such a system being adapted for operation over ordinary wired lines, such as telephone lines or cables.

Another object is to provide a radio telephone system having a receiving circuit in two portions, one portion of which is located remotely from the other portion and controlled by means of wired communication devices.

Another .object is to provide a radio telephone receiving system having directional antennae, and a receiv ng circuit divided into two parts, one part being located in the vicinity of the antennae and the other part being located remotely, with means for controlling the operation of the first part from the location of the second part, particularly as regards the selection of the desired directional antenna and the amplify ing system associated therewith. 7

Another object is to provide a radio telephone receiving system having a plurality of directional antennae and an amplifier connected to each antenna at one location, connected by wired lines to a second location, where means is provided for controlling the selection and operation of the particular antenna and amplifier, the second location having circuits for completing the reception and transformation of the radio signal into an audible signal.

Another object is to provide a radio telephone receiving system, as described above, wherein means is provided for automatically switching the audible signal to a land telephone line.

Another object is to provide a radio telephone system having a transmitter and a receiver interconnected bya simplified relay switching circuit in which a single relay performs the switching operations from thetransmitter to the receiver, and vice versa, this relay being operated in part by received carrier signals and in part by voice currents being transmitted.

Another object is to provide a radio receiving system having a nected to the loud speaker circuit during standby periods, and responsive to the reception of a low frequency audio tone from the transmitting station prior to each call, this being adapted to reduce the annoyance from static crashes during such stand-by periods when the receiving station is adjusted to high sensitivity while awaiting calls.

low pass audio filter circuit con- Another object is to provide a radio signalling system having a transmitter and a receiver interconnected through a switching system operated by a single relay, which in turn, is controlled by a pair of electronic tubes, one tube being responsive to the arrival of received carrier signals for actuating the relay in one direction, as for receiving, and the other tube being responsive to the arrival of transmitted voice currents for operating the relay in the other direction so as to place the transmitter in a transmitting condition.

Another object is to provide a method of controlling the selection of a radio receiver or transmitter by causing the voice currents and carrier wave signal currents to operate switching means for alternately switching in the receiver while switching out the transmitter, and vice versa.

In the drawings:

Figure l is a circuit diagram showing a portion of a radio telephone receiver located in the vicinity of a plurality of directional antennae;

Figure 2 is a circuit diagram of another portion of the radio receiving circuit located remotely from the circuit of Figure 1, and connected thereto by wired lines.

Figure 3 is a circuit diagram of a radio receiver and transmitter interconnected by an automatic switching arrangement, operated by a single relay responsive in part to voice currents and in part to received carrier signals.

General arrangement In general, the radio telephone system of this invention consists of a transmitter and a receiver, divided into at least two portions, one portion of the receiver being located in the vicinity of the antennae and the other portion being located remotely and connected thereto by wired lines having controlling devices associated therewith. In particular, the receiver preferably has two or more directional antennae, with an amplifier associated with each antenna, both amplifiers being connected to an oscillator circuit employing a fixed oscillator frequency, The selection of the particular antenna and amplifier is made through wired lines running from the receiver control station.

The receiver shown uses the superheterodyne circuit with a single frequency of a narrow band of frequencies, the intermediate amplifier being capable of being tuned. This tuned amplifier is located at the receiver control station, which is at a considerable distance from the receiving antennae and associated amplifiers. The signals amplified by the intermediate amplifier at the controlling station are, in turn, amplified by an audio amplifier and conducted either to a loud speaker or head phoncs, as desired. A transmitter is located at the receiver control station and selectively connected to a land telephone line by a relay-operated switching arrangement, the relay being operated in one direction by the plate current received from a tube responsive to receiving carrier signals, and operated in the opposite direction by a tube responsive to transmitting voice currents. The former tube opcrates the relay to place the receiver in connection with the land telephone lin and the latter tube operates the relay to place the transmitter in connection with the land telephone line.

Associated with the loud speaker circuit is a low pass filter system, which permits the passage of a low frequency calling tone from the distant: station, but filters out the higher frequency tones resulting from static. In this manner the static annoyance during stand-by periods is greatly reduced, the low pass filter system being arranged to be switched out by the operator when he prepares to receive the message signals from the calling station.

Hitherto, in radio telephone systems, it has been desirable to place thev receiving antennae at adistance from the transmitting station in order to avoid interferences from the transmitter. Under such circumstances, it has been usual to provide technical operators at both the receiving and transmitting locations, or alternatively to operate the transmitters by remote control from the receiving location in order to avoid the necessity of having technical operators in constant attendance at the transmitters. Such arrangements, however, are objectionable. either on account of the expense of maintaining operators at both stations, or because of the danger of damageto the transmitting equipment where no operators are present and where it is controlled remotely. Accordingly, it is preferable to have the operators at the transmitting location and the receivers operated by remote control. The present invention accomplishes this and enables the selection of a particular directional antenna from the remotely located receiver control station. These directional receiving antennae are provided to improve signalling conditions with mobile stations, such as ships at sea, when communicating with a particular ship in a certain direction.

Hitherto, when the transmitter has been switched into operation and the receiver switched out oi operation, a system employing two or more relays has been provided to accomplish this switching service, one relay being operated from the voice signals received by the radio receiver, another operated by the voice. signals received over the land telephone line, and a third operated by the carrier wave of the station whose messages are being received. This multiple relay system is exceedingly complicated, and liable to breakdowns, and in the present invention is replaced by a single relay operated in part by carrier signals and in part by voice currents to perform the necessary switching functions.

Hitherto also, in radio telephone stations, atmospheric static conditions have produced annoying noises in the loud speaker or head receivers while the operator has been standing by awaiting calls from distant stations. These static noises could not be avoided because of the fact. that the receiver mustv operate at full sensitivity at such times in order to avoid missing weak signals from distant stations. The constant static noises produce severe nervous strain upon the operators, and are reduced in the present invention by the use of low pass audio filters in the loud speaker circuits during stand-by periods. The mobile stations in calling the land station, first transmit a low frequency auoio tone prior to each call, this tone being passes by the filters and operating the loud speaker. The low pass filter system may thus be switched out and the receiver operated in a normal way to receive the message.

Receiver circuit The receiver circuit shown in Figures 1 and 2 consists, in general, of an antenna located portion shown i'n Figure 1, and a remotely located portion shown in Figure 2. The receiver employs the superheterodyne principle with the equipment divided in such a manner that the radio frequency amplifiers, oscillator and first detector are located in the vicinity of the an-- tennae, an intermediate frequency of the order of 300 to 400 kilocycles being transmitted over wired I Figure 2, where the intermediate frequency amplifiers, second detector and audio amplifiers are located. The radio frequency amplifiers are tuned to a fixed frequency or a very narrow band of frequencies because only a single frequency or narrow band of frequencies is to be received. Unlike the ordinary superheterodyne receiver, where the intermediate frequency is fixed and the oscillator frequency is tuned to be equal to the received frequency plus or minus the intermediate frequency, the present invention employs a fixed oscillator frequency in order to avoid the necessity of tuning the oscillator by remote control. In the present invention, therefore, the intermediate frequency is not constant but varies within the narrow band of frequencies to be received, hence, the intermediate frequency amplifier is arranged to be tuned.

Referring to the drawings in detail, Figure 1 shows the antenna located portion of the receiver circuit as designated by the numerals between I and I99. Figure 1 shows a plurality of directional antennae, two being shown, and designated I00 and IOI. These antennae are connected at the terminals I02 and I03 through coupling condensers I53 and I54 to the grid circuits of the tubes I01 or I08. Inductances I04 and I05 and variable condensers I06, connected across the inductances I04 and I05, permit the tuning of the grid circuits of the tubes I01 or I08 to the particular frequency which is to be received.

Thetubes I01 and I08 are connected, respectively, to tubes I09 and IIO in a circuit constituting a two-stage screen grid radio frequency amplifier for each of the antennae I00 and IN. The grid circuits of the tubes I09 and II 0 are inductively coupled by means of the inductances III and tuned by means of the variable condensers I I2. The usual resistors provided in such a radio frequency amplifying system are designated by the numerals II3 to H1, inclusive, these being lines to the receiver control station of duplicated for each of the two radio frequency amplifiers, generally designated III and H9, and associated with each directional antenna I00 and IN. Resistors I20 and I2I complete the amplifier circuit. By-pass condensers I22, I23, I24 and I25 are likewise provided.

The gain of these radio frequency amplifiers Ill and II! is controlled by varying the grid bias voltage from the remotely located receiver control station, this being done by cathode resistances' connected across the cathode by-pass condensers I25. The lines I26 and I21 run for thispurpose from thecathodeby-pass condensers I25 to the remote receiver control station, and connect up with the lines 226 and 221 in Figure 2. The lines 226'and 221 (Figure 2) are connected to a key switch 228, which controls the connection of either of the variable cathode resistors 229 or 230, thereby selecting the particular amplifier H8 or II9 and disabling the associated amplifier. The'adjustment of the cathode resistances 229 and 230 controls the gain of the radio frequency amplifiers H8 and H9 from the remotely located receiver control station.

Thus to increase the gain of the upper twostage amplifier II8 the resistance of the variable cathode resistor 229 between the line 226 and the ground connection 23I is decreased- To disable the upper amplifier II8 the key switch 228 is operated to open the circuit between the variable cathode resistor 229 and the line 226, at the same time closing the line between the variable cathode resistor 230 and the line 221. By variously operating the key switch 228 it is thereby possible to select either or both of the receiving antennae I00 or IOI, thereby making directional or diversity reception possible The variable cathode resistor 230 is similarly connected to the ground at 232. The circuit containing the lines 226 and 221, together with the key switch 228 and resistors 229 and 230, is shown and designated by the same reference numerals in Figure 3.

The outputs of the two radio frequency amplifiers Band II9 (Figure 1) are connected together at the terminal I28 and feed into the grid tuning inductance I29 of the first detector or mixer tube I30. A variable condenser I3I is pro.- vided for tuning this grid tuning circuit. Resistors I32 and I33 and fixed condensers I34 and I35 are provided in the circuits beyond the inductance I29. The first detector tube I30 also functions as an oscillator under the control of the crystal I36 having the resistor I31 bridged therearound. The oscillations of this crystal I36, in cooperation with the tuning circuit I38 having the inductance I39 and variable condenser I40, serve to convert the radio frequency signal from the amplifiers H8 or I I9 into the intermediate frequency of 300 to 400 kilocycles. The output of the first detector or mixer tube I30 is tuned to the intermediate frequency band by means of the inductance MI and variable condensers I42 and I43.

The transformer I M has the secondary winding connected to the transmission lines I44 and I45, .leading to the receiver control station (Fig ure 2), the same lines being there designated 244 and 245. The dimensions of the transformer I, particularly the secondary thereof, are carefully determined to procure the proper impedance matching with the transmission lines I44 and I45, which take the signal to the receiver control station shown in Figure 2. The transmission lines I44 and I45 may consist of paired linesin the ordinary telephone cable, this giving good results up to a length of several miles. Likewise associated with the circuit of the first detector or mixer tube I30 are the resistors 6,141 and I48 and the fixed condensers I49, I50 and I5I, together with the jack switch I52. In the tube I30 the crystal frequency from the crystal I36 is mixed with the radio frequency or signal frequency to produce a beat frequency between 300 kilocycles and 400 kilocycles, which is taken off in the transformer HI and transmitted to the impedance matching transformer 200 (Figure 2) over the lines I44, 244, Sand 245. The heater voltage for the various tubes (one filament only being shown for simplicity) is applied between the terminals I and I56 and the plate voltage between the terminals I51 and I58. The jack I52 provides means for measuring the oscillator anode current by plugging a meter into the circuit in tuning the oscillator.

The portion of the receiver shown in Figure 2, and termed the "receiver control station," contains the two-stage intermediate frequency amplifier, generally designated 20I, and connected into the impedance matching transformer 200.

Thetwo-stage amplifier 20I contains the electronic tubes 202 and 203, the coupling transformer 204, the output transformer 205 and the second detector tube 206. The portion of the receiver at the receiver control station is, in effect. a tuned radio frequency receiver using tuned circuits in both the grid and plate circuits. The transformers 200, 204 and 205 have cores of powdered high frequency iron and are tuned to the intermediate frequency corresponding to the signal to be received by means of the ganged variable condensers 201, 208, 209, 2I0 and 2| I. Additional variable condensers 2I2 to 220 and 231 serve to pretune the various circuits so that the ganged variable condensers 201 to 2II will track over the entire scale. Additionally provided are the fixed condensers 22I to 225 and 233 to 236, the resistances 238 to 243 and 246 to 250.

For supplying plate voltage the rectifier circuit containing the plate supply rectifier tube 25I is provided together with the transformer 252 connected to the power lines 253 and 254 by way of the line switch 255. The resistor 256 and chokes 251 and 258, together with the fixed condensers 259 to 262, inclusive, complete the rectifier circuit. To the resistors 263 and 264 are connected the potentiometer 265, the adjustment of which serves to adjust the sensitivity of the receiver. This potentiometer 265 is located in the amplifier cathode circuit, as is seen from Figure 2. The second detector tube 296 is connected as a rectifier, and supplies negative voltage for the automatic volume control of the amplifier by means of the bias voltage passing through the resistor 249 to the tubes 202 and 203. This bias voltage also passes through the resistor 250 to the line 266 for connection to the voice terminal equipment shown in Figure 3.

The second detector tube 206 also supplies audio voltage to the audio frequency amplifier, generally designated 261 and having the audio amplifier tubes 268 and 269, together with the audio transformers 210 and 21I. The audio voltage from the second detector tube 206 is fed to the potentiometer 212, the arm of which is connected to the grid of the first audio tube 268. The potentiometer 212 serves as the audio volume control, and has associated therewith the fixed condenser 213. Additional resistors 214, 215 and 216, together with fixed condensers 211, 218, 21!. and 280 and a potentiometer 28I complete the audio amplifier circuit. The output of this twostage audio amplifier 261 is taken off at the lines 282 and 283.

Voice terminal circuit In Figure 3 the circuit shown in Figure 2, consisting of the receiver control station, is shown by the same reference numerals. The entire amplifying and detecting system, however, and including the radio frequency amplifier 2M, audio frequency amplifier 2" and rectifier circuit, is indicated diagrammatically and designated the receiver" 284. This numeral 234 refers to all of the equipment shown in Figure 2 excepting the circuit 226 to 232, controlled by the key switch 223 for selecting and controlling the receiver circuit shown in Figure l. The latter may be mounted upon or near the masts of the antennae and requires no constant attendance of an operator.

The output of the receiver 284 from the lines 232 and 233 (Figure 3) is connected through the normally closed contacts of the key switch 300 to the low pass filter circuit, generally designated 3, and consisting of the transformers 302 and 303, the inductances 304 and 306 and the fixed condensers 306, 301 and 303 and an amplifier 309, which in turn, is connected to a loud speaker 3). The key switch 3 is provided for cutting the low pass filter circuit 3 out of the circuit of the loud-speaker 3M.

The low pass filter circuit 3M eliminates most of the static noise, but passes the low frequency tone transmitted from the ship prior to each call. When the operator hears this tone from the loud-speaker 3" he may operate the key switch 3 to cut the filter circuit 3 out of the circuit of the loud-speaker 3lll, or else he may operate the key 3" to disconnect the filter circuit 3M and loud-speaker 3ll, together with its amplifier 3M, and simultaneously to connect the output lines 232 and 233 of the receiver 234 to the telephone head phones 3|2.

Beyond the key switch 330 the receiver output lines 232 and 233 are connected into the primary of a transformer M3, the secondary of which is connected to the lines 3 and3l5, respectively. The line 3 runs to the key switch 318 by which the relay 3" may be cut into or out of operation. The relay 3|! is provided with a relay-operating coil 3l3, connected at the terminal 3'9 to a suitable source of positive current, and on its other side connected to the line 320 leading to the terminal 3. The line 315 from the transformer H3 is connected beyond the relay 3" to the repeat coil or transformer 322 by way of the line 323. From the opposite terminal of this winding of the repeat cell 322 the line 324 runs to the opposite terminal of the relay 3". The other winding of the repeat coil 322 is connected to the land or wired telephone lines 325 and 326, leading to the land telephone system with which itmay be desired to connect the radio telephone system for direct communication between a ship station and a land telephone subscriben.v

Beyond the key switch M6 and relay 3" the lines 321 and 324 run to one winding of the transformer 329, the opposite winding of which is connected by the lines 333 and at to the transmitting amplifier 332. Theoutput lines 333 and 334 of the'latter run to the attenuation device 335. from which the lines 336 and 331 run to the radio transmitter 333. The details of the radio transmitting system are immaterial to the present invention. The lines 334 and 331 are connected by the lines 333 and 343 to one winding of a transformer 3", the other winding of which is connected into the plate and grid, circuit of a vacuum tube 342, forming a part of the switching circuit, generally designated). Besides the tube 342 the switching circuit 343 contains electronic tubes 344 and 345, having their plates connected through the milliammeters 343 and 341 to the terminal 32! of the line 323 leading to the operating coil 3l8 of the relay 3". In this manner plate current from either of the tubes 344 or 345 will energize the relay coil 3|. and operate the relay 3| I. v a

The tube 345 is hereinafter called the voice in its cathode circuit. The tube 344, on the other hand, hereinafter called the carrier tube, is normally biased by means of the potentiometer 343 in its screen grid circuit so as to null a wedetermined amount of current, for example, two milliamperes. This current in an operated condition (Figure 3) shunting out the radio receiver output circuit and leaving the land telephone lines 323 and 324 connected to the radio transmitter input lines336 and 331. The switching circuit 343 is completed by the fixed condenser 350 and the resistors 35l to 384, inclusive. Between the resistors 333 and 334, the terminal 355 is connected to the line 3 leading to a source of positive 13" voltage, such as 300 volts, this connection being similar to that of the terminal 3|! of the relay-operating coil 3", and completing the relay-operating coil circuit.

The control grid of the carrier tube 344 is connected to the automatic volume control voltage of the radio receiver 284 through the line 2, previously mentioned. The tubes in the receiver which have this automatic volume control voltage applied to their grids are of the variablemu type and require a high bias voltage for plate current cut-off. The tube 344, which may be of the type known commercially as the type 606. is an abrupt cut-oil tube. Accordingly, when a normal signal is received from the radio receiver 234 enough bias voltage will be generated to completely block the carrier tube 344. Since the carrier tube plate current normally holds the relay 3i! operated to connect the land telephone lines 323 and 324 with the radio transmitter 333, as shown in Figure 3, every time a signal is received by the radio receiver 234 the voice-controlled carrier" will set up enough bias voltage to block the carrier tube 344, which in turn, allows the relay 3" to drop. The carrier is transmitted by the remote station only when talking, the transmitter being put into operation by voice signals.

when the relay drops the output of the receiver 234 is automatically connected directly to the land telephone lines 323 and 324, and the radio transmitter input is automatically shunted out. When the radio telephone party at the distant station stops talking, the carrier disappears, the automatic volume control voltage over the'line 266 drops, and the carrier tube 344 draws current. This current energizes the relay coil 3" to operate the relay 3", and the land telephone party is again connected to the radio transmitter 333. when the land telephone party begins to talk a small portion of the audio input to the radio transmitter 338 is fed through the lines 339 and 344 to the transformer 34l, thence to the tube 342, which rectifies this voltage and places the rectified voltageon the grid of the voice tube 3.

This rectified voltage from the tube 342 operates to make the grid of the voice tube 343 less negative. or in the case of strong signals, actually positive with respect to the cathode of the voice tube 343. This change inthe grid voltage on the grid of the voice tube 345 causes plate current to fiow from the plate thereof, which supplements holds the relay 3".

loudspeaker am, wher it sounds'the 10W tonecarrier tube 344, thereby causing the armature 3" to maintain its contact with the front or lower contact member; even though static crashes might occur while the land telephone party is talking. The attenuator 335 serves for adjusting the-speech volume fed into the radio transmitter.

' Operation Much of the. operation of the radio system of this invention has been described in connection with the respective circuits; When the operator at the receiver control station,-in-Figure 2, de-

sires to communicate .with a particular ship in a knowndirection, he selects-either or; ,both of the directional receiving antennae ,IM or llby manipulating'the key switch 223,'in the manner I4 I' and over the lines. I44,

. justed. from .the. receiver controlstation;v

in or out of operation previously described. This automatically. connects the radio frequency amplifier H8 or- H9 with the cathode variable resistors 229 or 230, by which the gain of each amplifier may be ad- When a ship calls, it first sends out a low audio tone,,w hich isreceived over one of. the antennae 10 0 or ill], amplified through the selected radio frequency amplifier. I I3 or. l l9, and mixed in the first detector tube l3!) with the crystal frequency from the crystal I36 to produce a beat frequency between 300 andg100 ,kilocycles. -This passes through the impedance matching transformer 145, 244 and 245, through the impedance matching transformer 2ll0to the intermediate frequency, amplifier 2M, whichhas been adjusted by means of the ganged ,condensers 201 to-2ll to receive the ship's fre- 232 and 283, through the key switch 300 and low pass filter system 31H to the amplifier 309 and This warns the operator of the presence of'the signal and ,he then manipulates thekey 3 to .cut out the low pass filter circuit 30l from the loud speaker 3lll so as to.hear the message signals directly, overthe loud speaker-3H], or else he manipulates the keyswitch ,300 to transfer the'message signals to his head phones 3I2. The ship then transmits the message signals upon the selected frequency, and these message signals operate the switching system 343, in the manner previously described, to actuate the relay 3l1 in such a manner as to connect the land telephone lines 325 and 326 to the radio receiver 234 (Figure 3). The relay 3l6, however, may be placed by manipulating the key switch 3l6, The land party then' listens. to the message. i I

When the party on the ship ceases talking, the relay 3|i automatically operates in response to the action of the switching system 343, connecting'the' land telephone party to the radio trans,- mitter 338. When the land telephone party begins'to talk the audio input current, which passes through the transformer 3 to the tube 342 of the'switching circuit 343, causes plate current to flow in the voice-operated tube 345 which supplementsthe current through the rel?" coil 3! from the carrier tube 344, thereby holding the relay 311 against its lower contact, irrespective mitter 338 to the land telephonelines 325 or 326. The voice currents produced in theland lines 325 and 326are rectified by the tube 342, and applied to the voice tube 345 in such a manner as to hold the relay 3!! in the transmitting position so long as the voice currents fromthe land telephone party continue to arrive over the lines 325 and 326.

When a carrier wave arrives in the radioreceiver '284, however, a negative voltage is generated thereby, which is conveyed to the carrier tube 344 in such a manner as to cut off its plate current and the relay 3" is released to make contact with its upper terminal. When neither the carrier tube 344 nor the voice tube 345 pulls current through the relay coil 3|8, the radio of the radio frequency detector circuit to a condition where gangingit with the amplifier grid and plate tuning condensers is made possible. 'On diode detectors the load is quite different from the load on the amplifier grid and plate circuits, and hitherto this has made it quite difficult to gang the diode tuning condenser with the amplifier grid and plate tuning condensers. In place of therelay 3!! switching by means of tubes, copper oxide rectifiers or other analogous devices might alternatively be employed. It will also be understood that the signal announcing means responsive to low audio frequency signals only may include loud speakers mechanically tuned to respond to low frequencies only, or mechanical low pass filters and other devices, excluding high audible frequencies and passing only low audible frequencies.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desired to secure by Letters Patent, is:

1. In a radio receiver, a plurality of directional antennae and an amplifier connected to each antenna at a first location, a tuner at a second location, wired means interconnecting said amplifier with said tuner, control means at said second location operable over said wired means for controlling the operation of said antenna located amplifier, and-means at said second location for selectively connecting one of said directional antennae with said tuner.

2. In a radio receiver, a plurality of directional antennae and an amplifier connected to each antenna at a first location, a tuner at a second location, wired means interconnecting said amplifier with said tuner, control means at said second location operable over said wired means for controlling the operation of said antenna located amplifier, and means at said second location for selectively connecting one of said directional antennae and one. of said amplifiers with said tuner.

3. In a radio receiver,r-a plurality of directional antennae, a preliminary radio receiving circuitconnected thereto and including a radio frequency amplifier for each antenna and a del tector-oscillator, a final radio receiving circuit located remotely therefromand including an intermediate frequency amplifier, vwired means connecting said preliminary and final circuits,

means at said final circuit and operable over 10. said wired means for selectively connecting one of said directional antennaeand its associated amplifier to said final receiving circuit.

4. In a radio receiver a plurality of directional antennae, a preliminary radio receiving circuit 15 connected thereto and including a'radio frequency amplifier for each antenna and a deteeter-oscillator, a final radio receiving circuit located remotdy therefrom and including an intermediate frequency amplifier, wired means 90 connecting said preliminary and finaicircuits,

meansatsaidfinal circuit and operabieoversaid' wired means for selectively, connecting one of said directional antennae and'ltsassociated am-,

plifier to said final receiving circuit, and control means at said final circuit for controlling the energization of said preliminary circuit.

5. In a radio receiver, a plurality of directional antennae, a preliminary radio .receivingcircuit connected thereto and including a radio frequency amplifier for each antenna. and a detector oscillator, a flanal radio receiving circuit located remotely therefrom and including an interme-' diatefrequency amplifier, wired means connecting said preliminary and final circuits, means at I said nmii circuit and operable over said wired means for selectively connecting one of said directional antennae and its assoclatedamplifier to said final receiving circuit, and control'means at said final circuit for controlling the actuation of said radio frequency amplifier.

6. Ida radio receiver, a plurality of directional antennae, a preliminary radio receiving circuit connected thereto and including a radio frequency amplifier for each antenna and a detectoreoscillator, a final radio recelvingcircuit located remotely therefrom and including an intermediate frequency'amplifler. wired means connecting said preliminary and final circuits, meansat said final circuit and operable over said I wired means for selectively connecting one of said directional antennae and its associated amplifier to said final receiving circuit, and control means i at said final circuit for controlling the gain of said radio frequency amplifier.

ll 7. In a radio receiver, a plurality of directional antennae, a preliminary radio receiving circuit connected thereto andincluding a radio frequency amplifier for each antenna and a detector-oscillator, a final radio receiving circuit Q located remotely therefrom and including an intermediate frequency amplifier, wired means connecting said'preliminary and final circuits, means at said final, circuit and operable over said wired means for selectively connecting one 08 of said directional antennae and .its associated amplifier to said final receiving I circuit, said intermediate frequency amplifier having tuning means associated therewith for tuning the signals from saidradio frequency'amplifier.

1o 8. In a radio system, a receiving antenna adapted to operate with a transmitting antenna positioned sufiiciently remote from one another to avoid interference and adapted to be connected selectively to a common wire line. a radio 1 receiving circuit connected to the receiving. an-' the said transmitting and receiving antennae being of theamplifiers in the tenna, said circuit having two portions one of which is positioned at the receiving location and the other portion is positioned at the transmitting location. means positioned at the said transmitting located portion of the receiving circuit 5 for controlling the operation of the located portion of the circuit.

9.1a a radio system. a receiving antenna adapted to operate with a transmitting antenna positioned suiiiciently remote from one another 10 to avoid interference and adapted to be connected selectively to a common wire line, a radio receiving circuit connected to the receiving anreceiving tenna, said circuit having two'portions including grid-controlled amplifiers. one of said portions being positionedat thc'receiving location and the other portion positioned at the transmitting location, means positioned at the said transmitting located portion of the receiving circuit for controlling the grid bias of the amplifiers of the receiving located portion of the circuit. 10. In a radio system, a plurality of receiving antennae adapted to operate with a transmitting antenna and positioned suiiiciently remote from transmitting antennato avoid interference,

adapted to be connected selectively to a common wire circuit, a receiving circuit having two por tions one of; which is positioned at the transmittinglocation'and-the other at the receiving location, means in the 'ving circuit portion at the transmitting location for selectively connecting'the receiving-circuit portion at the receiving location to each of the receiving antenna. v

ii. In a radio system, a plurality of receiving 85 antennae adapted to operate with a transmitting'antenna and positioned sufficiently remote 'means in the receiving circuit portion at the transmitting location for selectively connecting the receiving circuit "portion at the receiving location to each of the receiving antennae, means in the receiving circuit portion at the In transmitting-location for controlling the gain receiving circuit portion at thelreceiving antennae.

' 12. In a radio system, a receiving antenna 'adapted to operate with a transmitting antenna ss positioned sufiiciently remote from one another to avoid interference and adapted to be connected selectively to'a common wire circuit, a

- receiving circuit having two portions one of which is positioned at the receiving location and 00 the other is positionedatthe transmitting location, the receiving circuit portion at the receiving location comprising fixedly tuned thermionic devices and a fixedly tuned detector-oscillator, the receiving circuit portion at the transmitting location including variably tuned thermionic devices whereby the tuning of the receiving circuit as a whole is eifected from the transmitting location. v

13. In a radio system, a receivingantenna 7Q adapted to operate with a transmitting antenna positioned sumciently remote from one another to avoid interference and'adapted to be connected selectively to a common wire circuit, a

a receiving circuit having two portions one of it which is positioned at the receiving location and the other is positioned at the transmitting location, the receiving circuit portion at the receiving location comprising fixedly tuned thermionic devices and a fixedly tuned detector-oscillator, the receiving circuit portion at the transmitting location including variably tuned thermionic devices and further including devices for controlling the amplifier gain of said thermionic devices at the receiving location whereby the tuning of the receiving circuit as a whole and the amplifier gain of the receiving circuit are con- 5 trolled from the transmitting location.

DONALD A. HEISNER. 

